The present invention relates to a plasma treating apparatus and a plasma treating method in which a plasma treatment is carried out over a semiconductor substrate such as a silicon wafer.
In a process for manufacturing a silicon wafer to be used in a semiconductor device, a thinning work for reducing the thickness of a substrate is carried out with a reduction in the thickness of the semiconductor device. The thinning work is carried out by forming a circuit pattern on the surface of a silicon substrate, and then, mechanically polishing the back of a circuit formation face. A plasma treatment is carried out in order to remove, by etching, a damage layer generated on the polished surface of the silicon substrate by the mechanical polishing after the polishing work.
In the plasma treatment, the silicon wafer is to be held in such an attitude that a surface to be treated (a back face) is turned upward. For this reason, the silicon wafer is held in such an attitude that the circuit formation face side is turned toward the mounting surface of a substrate mounting portion. At this time, a protective tape is stuck on to the circuit formation face in order to prevent a circuit from being damaged due to a direct contact with the mounting surface.
As a method of holding the silicon wafer, there has been known a method using electrostatic adsorption. In this method, the silicon wafer is mounted on a substrate mounting portion in which the surface of a conductor is coated with a thin insulating layer, a DC voltage is applied to the conductor to cause the surface of the substrate mounting portion to be an electrostatic adsorption surface, and a coulomb force is applied between the silicon wafer and the conductor provided under the insulating layer, thereby holding the silicon wafer in the substrate mounting portion.
In the case in which the silicon wafer having the protective tape stuck thereto is held by the electrostatic adsorption, however, the coulomb force acts with an insulating protective tape provided in addition to the insulating layer. As compared with the case in which the silicon wafer is directly bonded hermetically to the electrostatic adsorption surface without the protective tape, therefore, the electrostatic adsorption force is small and a sufficient holding force cannot be obtained in some cases. Also in the case in which a resin layer is formed for sealing or wiring over the surface of the silicon wafer and the resin layer side is hermetically bonded to the electrostatic adsorption surface to carry out the electrostatic adsorption, furthermore, the same problem arises.